At present the primary commercial method for preparing methylsiloxanes is by the hydrolysis of methylchlorosilanes to give methylsiloxanes and aqueous hydrogen chloride (HCl). The latter is reacted with methyl alcohol (MeOH) silicon (Si) to give Me.sub.x SiCl.sub.4-x. The chlorine cycle constitutes three steps; (1) hydrolysis to give HCl; (2) reaction of HCl with MeOH to give MeCl; and (3) reaction of MeCl with Si. It would be highly desirable to reduce this to a two step process in which the chlorosilane is reacted with MeOH to give the siloxane and MeCl. Reactions of chlorosilanes with MeOH to give siloxanes are not new.
U.S. Pat. No. 3,803,195 shows the reaction of MeOH with Me.sub.x SiCl.sub.4-x by a countercurrent flow method in which the column is packed with an essentially inert and acid resistant packing material. The patent states Col. 4, line 6 that catalytic agents such as Lewis-acids and cation exchange resins in the H-form may be used with the packing materials, but the use of such materials is not desirable and should be avoided. When the reaction was run with Me.sub.2 SiCl.sub.2, the product was ##STR1##
U.S. Pat. No. 2,556,897 discloses a liquid phase reaction of Me.sub.2 SiCl.sub.2 with MeOH. No catalyst is suggested. The product resulting was a viscous oil.
U.S. Pat. No. 2,741,630 reacts Me.sub.2 SiCl.sub.2 with MeOH at a temperature of at least 175.degree. C in the presence of ZnCl.sub.2 on silica gel. As pointed out by U.S. Pat. No. 3,803,195 use of ZnCl.sub.2 promotes cleavage of Me from Si.
It is the object of this invention to provide an economical method of producing siloxanes and MeCl which involves low yields of Me.sub.2 O and high yields of siloxane. Another object is to provide a method of producing primarily cyclic diorganosiloxanes and especially cyclotrisiloxanes without significant methyl cleavage.